The intertidal barnacle Balanus zhujiangensis Ren, 1989, is reported from Okinawa, Japan, for the first time. A supplementary description of this species is provided, and the specimens are compared to those from the Zhujiang River estuary which empties into the South China Sea. Several morphological characteristics of the shell, mouthparts, and armature of cirrus III suggest that B. zhujiangensis is related to the B. amphitrite complex rather than to B. trigonus by consistently having but a single row of pits on the external surface of the scutum and lacking an adductor ridge. The presence of scutal pits is interpreted as a means of facilitating the transmission of light through the valve thereby allowing the photoreceptors to detect changes in light intensity while the operculum is closed.